<html>

	<head>
		<script type="text/javascript">
			function getIndex() {
				var x = document.getElementById("mySelect")
				alert(x.selectedIndex)
			}
		</script>
	</head>

	<body>

		<form>
			Select your favorite fruit:
			<select id="mySelect">
				<option>Apple</option>
				<option>Orange</option>
				<option>Pineapple</option>
				<option>Banana</option>
			</select>
			<br /><br />
			<input type="button" onclick="getIndex()" value="Alert index of selected option">
		</form>

	</body>

</html>